Search Results (2,133)

Gleeble-3800 thermal simulation testing machine was adopted to investigate the evolution laws of microstructure and properties in the coarse-grained heat-affected zone (CGHAZ) of pipeline steels with different Cr mass fractions (0.2, 0.5, 0.8 wt.%) under welding heat inputs ranging from 8 kJ/cm to 20 kJ/cm. Combined with optical microscopy, scanning electron microscopy and electron backscatter diffraction, the coupled influencing mechanism of heat input and Cr content on the properties of CGHAZ was systematically analyzed. The results show that as the Cr content increases, the range of valid welding heat input for maintaining satisfactory CGHAZ impact toughness gradually narrows with increasing Cr mass fraction of the steel. Specifically, the 0.2Cr experimental steel maintains high toughness under a thermal input ranging from 8 to 20 kJ/cm, the 0.5Cr experimental steel exhibits relatively high toughness in the range 8 to 13 kJ/cm, while the 0.8Cr experimental steel shows high toughness only at 15 kJ/cm. The coupled effect of weld heat input and Cr content on CGHAZ properties originates from a combination of microstructural composition types, phase fractions, substructures, and grain sizes. Increasing the heat input and Cr content leads to a reduction in the bainite ferrite with superior toughness and an increase in the large-sized granular bainite with inferior toughness. Meanwhile, the effective grain size of the overall microstructure first decreases and then rises. Grain coarsening and an increased fraction of Martensitic/Austenitic (M/A) constituent are the key factors responsible for the deterioration of CGHAZ toughness in deep-sea oil and gas transportation pipeline steel. Full article

In this work, an adaptive fixed-time dynamic triggered control issue for interconnected power systems under Denial-of-Service (DoS) attacks is investigated. Such attacks would impede the transmission of sensor signals in interconnected power systems, precipitating a severely unstable power supply or even paralysis. To effectively confront this challenge, an adaptive switching neural network state observer is designed. The observer can maintain the output of the observation state under both attack conditions and normal conditions, thereby compensating for the adverse effects of DoS attacks on interconnected power systems. Meanwhile, a nonlinear fixed-time filter is constructed, which not only obviates the complexity explosion issue but also enhances the convergence capability of interconnected power systems. Moreover, a dual dynamic parameter threshold Event-Triggered Mechanism (ETM) is developed. Influenced by multiple dynamic parameters, this mechanism achieves a more precise control of triggered conditions, drastically conserving the communication resources of the interconnected power systems and preventing the occurrence of Zeno behavior. Ultimately, the effectiveness of the proposed methods is demonstrated by the simulation results. Full article

The history of steel rail manufacturing at the Hanyang Iron Works in China is briefly summarized first in this paper. The chemical composition, microstructure, inclusions, and mechanical properties of the manufactured rails were then systematically analyzed. The progress of manufacturing process evolution and the enhancement of product quality are elucidated through this study. The chemical composition of steel rails produced by Hanyang Iron Works in its initial stage (before 1904) was characterized by low carbon content (0.13–0.22 wt.%) and high phosphorus levels (P ≥ 0.15 wt.%). Inclusions were primarily identified as sulfides (MnS) and composite inclusions of sulfides and silicates (MnS·SiO₂). The microstructure consisted of a large amount of ferrite and pearlite. Following the technical transformation from 1905 to 1908, dephosphorization was achieved and the composition control of the steel rails was optimized. The carbon content of the rails was increased to above 0.48 wt.%, while the phosphorus content was significantly reduced (P ≤ 0.10 wt.%). The inclusions were identified as sulfides (MnS) and composite inclusions consisting of sulfides and aluminum oxides (MnS·Al₂O₃). The microstructure was transformed into a combination of a small amount of proeutectoid network ferrite and pearlite. The mechanical performance of the steel rails was substantially improved via the implementation of technological upgrades at the Hanyang Iron Works. A tensile strength of 800 MPa grade was achieved in some rails, which constitutes a 200 MPa increment over the strength of rails from the early production period. A transition in the fracture morphology of tensile specimens was observed, shifting from large and shallow dimples with a small amount of cleavage fracture to small, shallow dimples combined with predominant cleavage fracture. Full article

Occupational health and safety (OHS) malpractices may increase the risk of occupational injuries and are a significant public health problem in the iron and steel industries, often leading to disability and death. Information on OHS practices related to occupational injuries in the iron and steel industries is limited in many countries. This study aimed to assess OHS practices in relation to occupational injuries among workers in the iron and steel industries in Tanzania. A cross-sectional study was conducted among 321 production line workers. Data were collected through interviews, using a structured OHS questionnaire and the modified International Labour Organization (ILO) injury assessment tool. A total of 209 workers had experienced an occupational injury in the past year. According to univariate regression analyses, the safety practice variables ‘safety inspections’ and ‘use of personal protective equipment’ were significantly associated with occupational injury. However, after adjusting for sociodemographic and organizational factors, including years of work experience, work section, daily working hours, and shift work, these associations were no longer statistically significant. Working in the rolling mill, having less than four years of work experience, working more than 10 h per day, and performing shift work were significant predictors of occupational injuries. These factors attenuated the associations between safety practices and occupational injuries. The severity of injuries was found to be related to the accessibility of PPE. The findings suggest that work experience and organizational characteristics play a critical role in shaping occupational injury risk, highlighting the need for multifaceted interventions that integrate effective safety practices, work experience and organizational measures to improve worker safety in Tanzania’s iron and steel industry. Full article

Steel production contributes significantly to global emissions, making its decarbonization essential. Electrified steelmaking based on electric arc furnaces (EAF) using hydrogen-based direct reduced iron (H₂-DRI) and scrap is a promising pathway. This study analyzes how the H₂-DRI:scrap ratio affects electricity demand, CO₂ emissions, slag formation, and oxygen management. To address limitations of approaches based on aggregated data and linear scaling assumptions, a detailed bottom-up mass and energy balance model is developed, explicitly resolving process interactions between electrolysis, direct reduction, and EAF steelmaking. Eight H₂-DRI:scrap ratios ranging from 0:100 to 100:0 are evaluated. Electricity demand increases from 1.1 GJ/t_Steel (0.31 MWh/t_Steel) for scrap-based operation to 13.9 GJ/tSteel (3.86 MWh/tSteel) for fully H₂-based production, largely driven by hydrogen generation. Consequently, emissions strongly depend on electricity carbon intensity, with reductions of up to 95% under renewable supply. Electrolytic oxygen can fully cover process demand at ~10–13% H₂-DRI, enabling system integration benefits. A sensitivity analysis evaluates the influence of key process parameters on electricity demand, CO₂ emissions, and oxygen management, demonstrating the robustness of the proposed modelling approach. Full article

For multi-permanent magnet synchronous motors (multi-PMSMs) with nonlinearity and uncertainty, an event-triggered nonlinear adaptive PI control is proposed. To enhance the synchronization of multi-PMSMs, a coordinated control strategy is implemented. On the basis of this, a nonlinear adaptive PI control is proposed to address the tracking of the speed of the PMSMs, and the uncertainty signal is estimated by designing an adaptive law. Furthermore, an adaptive event-triggered control mechanism is presented to update control signals in real time, reducing communication resource consumption while maintaining ideal performance. Simulation results on a four-PMSM ring-coupled system demonstrate that the proposed event-triggered mechanism reduces the number of control signal transmissions by up to 92.1% compared with time-triggered sampling, while maintaining comparable control accuracy. Full article

This study presents a novel, low-temperature thermochemical activation process for the selective extraction of Cr and V from carbon steel EAF (CH1) and FeCr (CH2) slags at temperatures of up to 600 °C. Of the twelve reagents tested, NaOH was identified as the optimal alkaline agent for Cr activation at 500 °C, achieving extraction yields of 61.6% for CH1 (slag-to-reagent ratio of 12:8 g) and 80.6% for CH2 (ratio of 12:16 g). KOH at 400 °C was the most effective reagent for V extraction, yielding 89.4% for CH1 and 54.5% for CH2. Maximum metal concentrations were achieved after only five minutes of leaching at 60 °C. The process exhibits high selectivity; primary matrix components (Fe, Si, Al, Ca, Mg) either do not leach or only leach in negligible amounts. Iron forms insoluble oxides, and calcium converts into stable calcite, while magnesium is bound in the form of hydrotalcite specifically in the CH2 slag leaching residue. The CaCO₃ content was proven to be a crucial parameter determining the activation efficiency and effective transformation of Fe-Cr-V phases. This procedure enables the recovery of clean Cr and V leachates, while the residual mineral-rich fraction offers potential for various industrial applications in a closed-loop slag recycling process. Full article

Budget overruns driven by unpredictable building material prices are a persistent challenge in emerging economies, yet reliable price forecasting tools for structural materials such as steel reinforcement bar (RFT) remain largely unavailable to building project teams. This study develops an Autoregressive Distributed-Lag (ARDL) model to forecast RFT prices in Egypt using macroeconomic leading indicators. A structured filtering pipeline—stationarity testing, Variance Inflation Factor (VIF) screening, and Granger causality testing—reduced 22 candidate variables to nine predictors: producer price index (PPI), loan rate (LR), discount rate (DR), Egyptian Stock Exchange Index (EGX30), money supply (M0), exchange rate (ER), iron ore prices (ORE), American stock index (S&P500), and Hang Seng Index (HSI). ARDL bounds testing confirmed cointegration across look-back periods (LBP) of 3, 6, and 9 months. Comprehensive diagnostics confirmed model stability, homoscedasticity, and the absence of serial correlation. The ARDL was benchmarked against an Ordinary Least Squares (OLS) baseline and a first-difference vector autoregression (VAR) model. Evaluated as genuine multi-step (dynamic) forecasts over the held-out crisis-period window, the 3-month model achieved an out-of-sample mean absolute error of approximately 5.9% in price terms, retaining a clear advantage over the OLS baseline at that horizon. The proposed framework provides quantity surveyors, cost consultants, and project managers with a practical tool for setting RFT budgets at the tendering stage and optimising procurement timing. It is transferable to other building materials (cement, structural steel sections, glazing) across emerging-market construction economies. Full article

The premature deterioration of reinforced concrete structures caused by steel reinforcement corrosion remains a major challenge to long-term structural durability. This study systematically investigates the effects of corrosion inhibitor dosage on the fresh properties, mechanical performance, chloride ion penetration resistance, and capillary water absorption of self-compacting concrete (SCC). The evolution of the pore structure is characterized using low-field nuclear magnetic resonance (LF-NMR) and X-ray computed tomography (X-CT), and the proportions of pores within different equivalent spherical diameter ranges are quantified. In addition, the microstructural characteristics are examined by scanning electron microscopy (SEM). The results show that the incorporation of the corrosion inhibitor increases the viscosity of fresh SCC, resulting in reductions in slump. In general, the corrosion inhibitor reduces both the compressive strength and splitting tensile strength of SCC, with the smallest strength reduction observed at a corrosion inhibitor dosage of 2 wt%. All mixtures containing the corrosion inhibitor exhibit lower electric flux and water absorption than the control mixture, indicating improved resistance to chloride ion penetration and capillary water ingress. The combined LF-NMR, X-CT, and SEM results indicate that an appropriate corrosion inhibitor dosage may optimize the spatial distribution of hydration products, refine the pore structure, reduce total porosity, and suppress the formation of macropores. Overall, a dosage of 2 wt% provides the most favorable balance among workability, mechanical properties, durability, and microstructural compactness. These findings provide experimental support and technical guidance for the mixture design of durable SCC used in aggressive environments, including marine and salt-lake regions. Full article

The conventional sulfidization–xanthate flotation of oxide copper minerals is often limited by reagent consumption and the mismatch between surface generation and sulfidization when sulfidization is carried out only during flotation conditioning. To address these limitations, this study proposes an in situ sulfidization strategy during the grinding stage and investigates the combined regulation of grinding media (conventional steel vs. 18% Cr cast iron) and atmosphere (ambient air vs. N₂ purging) on the flotation of a synthetic malachite–dolomite ore. Real-time pulp chemistry monitoring and ethylenediaminetetraacetic acid (EDTA) extraction indicate that the conventional grinding environment has two main disadvantages: Fe dissolution from steel media increases Fe-related surface contamination, while the air-ground pulp promotes the oxidation and consumption of active sulfidizing species. The combined use of high-Cr media and an N₂ atmosphere improved the chemical environment for grinding-stage sulfidization. Specifically, the high-Cr media reduced Fe release and associated surface contamination, while N₂ purging shifted the pulp to a lower-potential environment that was more favorable for preserving active sulfide species. Under standardized reagent conditions, the optimized in situ sulfidization protocol increased copper recovery from 29.79% to 57.47% and improved the concentrate grade from 9.71% to 11.11%. These results suggest that regulating the grinding environment can enhance in situ sulfidization flotation of malachite by reducing Fe interference and controlling pulp redox conditions, providing useful guidance for the efficient beneficiation of oxide copper minerals. Full article

Aluminium cast components have become increasingly important in overhead line construction, particularly for parts such as cantilevers, tensioning devices, and connectors. Since the 1950s and 1960s, the transition from steel and iron castings to aluminium has enabled significant weight reductions, simplified assembly processes, and improved corrosion resistance—key advantages for enhancing the operational safety and service life of overhead line systems. However, the lower operational and fatigue strength of aluminium castings compared to steel imposes stringent demands on design, material selection, and quality assurance. A thorough understanding of fatigue mechanisms and constraint-induced stresses under cyclic loads from wind and tensile forces is essential to preventing crack initiation and component failure. This paper demonstrates how material analyses, experimental testing, and the targeted application of relevant standards can ensure the operational reliability of aluminium cast components. Furthermore, existing gaps in current standards are identified, whose closure is vital to fully exploiting the potential of aluminium castings for durable, lightweight, and low-maintenance overhead line elements. Full article

Under China’s “carbon peaking before 2030 and carbon neutrality before 2060” targets, the low-carbon transformation of the ironmaking stage—which contributes approximately 70% of the CO₂ emitted per ton of steel in the dominant blast furnace–basic oxygen furnace (BF–BOF) route—is decisive for decarbonizing the steel industry. In contrast to earlier reviews that describe individual technologies in isolation, this review provides a structured, cross-technology synthesis: the main routes are classified into short-/medium-term low-carbon blast furnace technologies (hydrogen-rich carbon-recycling oxygen blast furnace, hydrogen-rich injection, biomass char injection and ultimate energy-efficiency measures) and medium-/long-term non-blast furnace technologies (hydrogen-based shaft furnace direct reduction, smelting reduction, rotary hearth furnace, fluidized-bed reduction and electric smelting reduction) and are then compared on a common set of quantitative indicators—CO₂ mitigation, specific energy and hydrogen demand, technology readiness level (TRL) and relative cost. On this basis, emerging hydrogen-based flash ironmaking, developed from the interdisciplinary integration of “iron and steel–non-ferrous metallurgy–hydrogen metallurgy–plasma”, is critically assessed, with a clear separation between laboratory/pilot feasibility and industrial readiness. We conclude that low-carbon blast furnace technologies, owing to low retrofit cost and high maturity, will dominate near-term mitigation, whereas hydrogen-based shaft furnaces and, in the longer term, hydrogen-based flash ironmaking define the pathway toward near-zero-carbon ironmaking—conditional on the availability of green hydrogen and low-carbon electricity and on overcoming key engineering barriers. Full article

Accurately identifying scrap steel yield rates remains challenging due to the diverse types, mixed sources of scrap, and complex furnace working conditions. This paper proposes a mechanism and data joint-driven identification method, and identification precision is enhanced by community division of a knowledge graph. Firstly, a knowledge graph for scrap charging is constructed, and the label propagation algorithm (LPA) is used to divide communities with similar charging patterns. Then, a physics-informed neural network is designed for each community to identify scrap steel yield rates. Finally, the shapley additive explanations approach is employed to assess and quantify the influence of these factors on scrap steel yield rates. Experimental results indicate the following: (1) The proposed model for scrap steel yield rate based on knowledge graph community division achieves the highest identification precision, with a Root Mean Square Error (RMSE) of 3.20 tons and a Mean Absolute Error (MAE) of 2.62 tons. (2) Compared with the baseline joint-driven model without community division, the proposed method reduces the MAE by 26.6% (from 3.57 t to 2.62 t) and significantly improves the hit rate within ±5 tons by 13.97 percentage points (reaching 87.55%). These improvements validate the effectiveness of the community-based divide-and-conquer strategy in handling complex charging patterns. Full article

Maritime transport contributes 2.9% of global greenhouse gas emissions, traditionally evaluated through operational fuel cycles while neglecting lifecycle impacts. This study redefines merchant ship recycling as a strategic front-end pillar for global decarbonization by assessing Embodied Carbon Trade-offs. Utilizing a mixed PRISMA systematic and semi-systematic methodology of literature from 2019–2025, we analyzed bulk carriers, container ships, and tankers across six thematic clusters. Our findings demonstrate that scenarios involving the potential decommissioning of up to 22.2% of the global merchant fleet exceeding 20 years of age could significantly mitigate lifecycle emissions by displacing primary iron-ore smelting with circular electric arc furnace marine-steel recovery. Crucially, this environmental dividend is non-linear and bound by regional energy matrices; under deeply decarbonized grids, this technological displacement can theoretically yield an upper-bound 72% emissions reduction, whereas fossil-heavy power supplies significantly diminish net mitigation margins. Practically, this research provides an operational roadmap for shipowners and regulators navigating the Hong Kong Convention and carbon border mechanisms. This work concludes that sustainable shipbreaking has the potential to function as an economically viable, strategic reservoir of low-carbon raw materials essential for achieving international net-zero targets throughout the entire shipping structural lifecycle. Full article

Self-lubricating iron-based composites produced by powder metallurgy are promising materials for reducing friction and improving component durability under dry-sliding conditions. In this study, three composites reinforced with graphite and/or graphene oxide (Fe10%Gr, Fe10%GO, and Fe5%Gr5%GO) were fabricated to evaluate the influence of solid lubricants on densification, hardness, and tribological behavior. Powders were uniaxially compacted at 500 MPa and low-temperature-sintered at 880 °C under an argon atmosphere. The tribological performance was assessed by pin-on-disk tests against an AISI 52100 steel ball. Pure Fe exhibited the highest hardness (approximately 97 HV) and a final porosity of 17.5%, whereas the lubricant-containing composites showed porosities ranging from 17.3% to 22.8% and lower hardness values of 45–60 HV. Despite the reduction in hardness, all lubricant-containing compositions decreased the coefficient of friction relative to pure Fe (~0.33). Fe10%Gr and Fe5%Gr5%GO exhibited the lowest friction coefficients, reaching ~0.08 and ~0.05, respectively, while Fe10%GO showed the highest wear rate (~1.1 × 10⁻² mm³/Nm). Among the compositions studied, Fe5%Gr5%GO showed the best friction–wear balance among the self-lubricating formulations, combining low friction and moderate wear due to a surface synergy where graphite promotes continuous low-shear lubrication while GO promotes the formation of a more compact and resilient protective tribolayer. Full article